1. Field of the Invention.
The present invention relates to railway trucks and other casting products, methods of making such castings, and to cores used in making such metal castings.
2. Description of the Prior Art.
In the past, in making hollow cast metal bodies, it has been known to use cores made of bonded sand supported in green sand molds to produce the hollow castings. The cores have been used to create the hollows or open spaces in the castings.
Cores have commonly been made in core boxes, typically having cope and drag halves that are brought together along a parting line. There is a cavity in the core box, and a mixture of sand and bonding material are introduced into the cavity and cured. The core box cope and drag portions are then parted along the parting line, generally being pulled apart vertically. Because of the need to pull the cope and drag portions apart, the sizes and shapes of the cores to be produced have been limited: the cores have not been able to have parts that would interfere with the movement of the cope portions away from the drag and with removal of the cores from the cope and drag portions. Thus, it typically has been necessary to produce several different cores that are later joined or placed together in the green sand mold.
In the case of cast metal sideframes for railway trucks, many different core shapes have been needed to produce the basic shape of the interior of the sideframes and bolsters. As shown in FIGS. 15-17, more than twenty cores have been required, with some different cores sometimes adhered together in a separate process step before being placed in a receiving cavity in the mold, and with many different cores and groups of cores separately placed in the mold. While some cores such as a window core and bolster opening cores have been supported on core prints, many of the cores have been supported on chaplets on the mold surface. In addition to the placement of the cores being a labor intensive operation, the use of such multiple cores has been problematic from a quality control standpoint. With so many joints between the faces of the multiple cores, there is a potential for many fins to be formed on the interior of the casting. To remove these fins through a finishing operation has been difficult since the fins are on the interior of the casting. Moreover, these fins create another potential quality control problem since they could give rise to stress risers that could form along the fins. Other potential quality control problems arise from the potential for shifting of the cores' positions in the mold prior to or during the casting operation. If the cores shift position, the thickness of the walls of the casting could vary from the design.
In addition, multiple cores may be so thin that core rods are required to be used to support the sand. These core rods add to the cost of the process and complicate cleaning of the castings.
Another problem can arise in connection with the friction plates at the back of the columns of the cast sideframe. Such plates are bolted to the columns through bolt holes in the columns. These bolt holes are along a joint on the interior side of the column formed by the mating cope and drag cores. Any misalignment of the cores along the joint could cause the metal to have a stepped surface at the bolt hole, resulting in the potential for uneven or improper loading of the bolt.
Another problem can arise in connection with areas of the sideframe around lightener holes and other openings in the sideframe wall. Metal fins can form around these openings, and sometimes form facing the interior of the casting. To finish such a casting by removing these fins may be difficult to accomplish manually since the fins are less accessible to the worker. In addition, it is very difficult to remove interior fins through automation.
Similar problems have arisen in producing cast metal bolsters for use in railway trucks. Like the sideframes, bolsters have hollow interiors, and have traditionally been made with multiple cores to form the interior walls and interior surfaces of the outer walls. Sixteen separate cores have been used to produce such castings, with cope and drag portions sometimes adhered to each other or juxtaposed along joints, as in the case of the sideframes cores, with chaplets supporting the cores on the mold surface, and with separate cores inserted into the cores to define holes for bolting side bearings and dead lever lugs to the bolster.
Similar problems as those outlined for sideframes have arisen with respect to quality control for bolsters. The positions of the cores on the chaplets may shift in the mold, creating the potential for making a casting with less than or more than desirable wall thicknesses. Bolster production has required that the multiple cores be placed in a mold in a labor intensive operation with multiple joints where stress risers could form. And like the sideframes, interior fins could form around lightener and other openings, fins that could be difficult and labor intensive to remove and that are not conducive to removal through automated finishing operations. Moreover, fins can form on the edges of the openings which can be stressed and damaged during the removal operation in the case of both sideframes and bolsters.
The present invention addresses various aspects of these problems in the prior art.